Preheat the oven to 180 C (350 F). Lightly grease a (9.25x5.25x2.75) loaf tin.
Combine flour, baking soda and salt in a bowl.
In a separate bowl, mash the bananas and add butter, brown sugar and eggs together and stir until well blended.
Stir banana mixture into flour mixture and add chopped walnuts and raisins, stirring continuously to moisten. Pour mixture into the prepared loaf tin.
Bake in preheated oven for 60 to 65 minutes, until a toothpick or knife inserted into the center comes out clean. Let stand for 10 minutes, and then transfer it to the wire rack to cool.